Computer numerical controlled machine tools such as routers used in the woodworking, plastics and nonferrous metal industries, typically consist of a base unit, a stationary or moveable workpiece support table mounted on the base unit, a stationary or moveable gantry mounted on or adjacent to the base unit, and a toolhead assembly mounted on a transversely disposed bridge member of the gantry. Either the table or the gantry is displaceable relative to the base unit longitudinally or along an x-axis, the toolhead assembly is displaceable transversely or along a y-axis and a tool is displaceable vertically or along a z-axis. The table or gantry, the toolhead assembly and the tool are displaced along their respective axes by feedscrews driven by servomotors. The motions of the various components of the machine are controlled by a controller which operates the various servomotors of the machine according to instructions of a program inputted into the machine.
Workpieces to be machined are positioned on the table of the machine and located in predetermined locations by the use of pop-up pins provided on the table or other means, and are held down by various means including clamps and vacuum systems. Vacuum systems may consist of conventional systems which are suitable for large production runs, and universal systems which are more suitable for short production runs. A conventional vacuum system generally includes a vacuum port provided in the workpiece support table, connected to a vacuum pump, and a vacuum fixture positioned on the workpiece support table about the vacuum port on which the workpiece is positioned. The fixture is provided with a peripheral rubber seal engaged by the workpiece positioned thereon, which permits the evacuation of air between the fixture and the workpiece to hold the workpiece in place. A universal vacuum system generally includes a table having a lower rigid plate, an intermediate plate having a recessed upper surface arranged in a grid pattern, an upper spoilboard formed of a porous material such as particleboard, closing the recess grid pattern in the intermediate board to form a plenum and a vacuum pump operatively connected to the plenum. As a vacuum is applied to the plenum, air is drawn through the particleboard to produce a low pressure zone on the surface of the particleboard, which functions to hold a workpiece positioned on the particleboard.
In machines of the type described, the workpiece support surface is normally horizontal and the axis of rotation of the tool is vertical. Consequently, machining operations on a workpiece positioned on the table of the machine normally can be performed only on a single face of the workpiece. To perform machine operations on additional faces of the workpiece, a separate toolhead having a different, dedicated angle of rotation of the tool, a separate pivotable toolhead or an adapter for a toolhead which displaces the angle of rotation of the tool must be made available, or the workpiece must be reoriented on the table to present a different face to be machined. The requirement of additional tools obviously is disadvantageous because of increased capital expense, and the requirement of a tool change or a reorientation of the workpiece along with attendant fixturing also is disadvantageous because of an increase in machine cycle times resulting in increased production costs. The use of additional toolheads or adapters has the additional disadvantage of having limitations in terms of positioning the tool bit close to the workpiece support surface without the table interfering with the toolhead assembly, as when drilling a horizontal hole in a side edge of a workpiece of shallow depth, and risking crashing the toolhead onto the table. Also, the orientation of workpieces on the table has the additional disadvantage of a limitation of the height of an elongated workpiece positioned on an end thereof due to the upper limit of travel of the tool. Accordingly, it is the principal object of the present invention to provide a machine tool of the type described which is readily capable of machining different faces of a workpiece without the requirement of additional or special toolheads or adapters for conventional toolheads, or any extensive or unworkable orientation of the workpieces.